1. Field of the Invention
The present invention relates to an aluminum radiator and a manufacturing a tank thereof.
2. Description of Related Art
In general, in a vehicle including an internal combustion engine, a heat generated during an operation of an engine is transmitted to a cylinder head, a piston, a valve, and so on, and an excessively high heat weakens a strength of parts, shortens a life span of the engine, or causes an abnormal combustion which leads to a knocking or a pre-ignition and thus lowers an engine output.
In addition, when the engine is cooled unstably, an oil film of a cylinder inner surface is cut, and an engine oil is changed in quality. As a result, a lubricating function deteriorates, and an abnormal abrasion is caused in the cylinder. Furthermore, the piston may be glued to an inner wall of the cylinder.
For the sake of the reasons, a water-cooled cooling device is installed in a vehicle in order to cool the engine.
The water-cooled cooling device circulates a cooling water to a cylinder block and a cylinder head by a water pump to lower a temperature of an engine. Such a water-cooled cooling device includes a radiator, a cooling fan, and a water temperature controller in order to radiate heat of a cooling water. Of these, the radiator is an apparatus which radiates a heat and cools a high temperature cooling water.
FIG. 1 is a perspective view of a conventional plastic radiator. FIG. 2 is a partially cut perspective view of the conventional plastic radiator. FIG. 3 is a cross-sectional view of the conventional plastic radiator.
The conventional plastic radiator 1 includes header tanks 2 and 3, a core 4, and a support 7.
The header tanks include headers 2a and 3a and tanks 2b and 3b, respectively. The headers 2a and 3a are spaced apart from each other. The tanks 2b and 3b are coupled to the headers 2a and 3a by a brazing and have a heat exchange medium passage formed therein, respectively.
The core 4 includes a plurality of tubes 4a and fins 4b arranged between the tubes 4a. The tube 4a is coupled to a pair of the header 2a and 3a and communicates with the passage of the tanks 2b and 3b. A heat exchange medium flows through the tube 4a. 
The support 7 is coupled to the headers 2a and 3a to support the most outer tube among the tubes 4a. 
Meanwhile, the core 4 and the headers 2a and 3a are made of aluminum, and the tanks 2b and 3a are made of a synthetic resin such as a polyamide. Since the headers 2a and 3a and the tanks 2b and 3b differ in material, the headers 2a and 3a and the tanks 2b and 3b are coupled by a mechanical coupling method.
In other words, the headers 2a and 3a include a plurality of tap portions 2c formed along an edge thereof and spaced apart from each other. A plurality of the tap portions 2c are bent to surround the tanks 2b and 3b, so that the headers 2a and 3a and the tanks 2b and 3b are firmly coupled.
A gasket 5 is interposed between the headers 2a and 3a and the tanks 2b and 3b to prevent a cooling water from being leaked.
However, the conventional radiator has the following disadvantages.
Firstly, the conventional radiator is difficult to recycle because components are made of different materials. For example, the core is made of aluminum, the gasket is made of a rubber such as an ethylene-propylene rubber (EPDM), and the tank is made of a plastic. Even though the core and the header made of aluminum are recycled, the core and the header have to be separated from the plastic tank for a recycling. Therefore, the work process number for a recycling is increased.
Secondly, an assembly process is complicated, and thus a manufacturing cost is increased. In order to prevent the cooling water from being leaked, a calking process is required that arranges the gasket and fixes the tank using the tap portions of the header.
Thirdly, a coupling between the header and the tank is relatively weak. Even though the tap portions of the header presses the tank made of a plastic, when an inner pressure of the radiator is increased, the tap portion becomes wider, thereby forming a crevice.
Further, when an interference between an appendage (e.g., a cooling water inlet/outlet or a vehicle body mounting pin) arranged necessarily in the tank and the tap portion occurs, since a calking for the tap portion is not performed, a non-calking portion is lower in strength than the other portions.
Fourthly, the plastic tank may be broken. Even though the tank is strong in brittleness and is excellent in strength, since the tank is not transformed, the cooling water may be leaked, and a crack may occur that affects an engine cooling. Such a crack results from either a pressure of the tap portion 2c pressing the tank during a calking process, a vibration of a vehicle body, a material characteristic, or an injection molding condition. However, there is no method to inspect a weak portion such as a crack until the radiator is completed, and thus a product reliability is lowered.
Fifthly, the header and the tank are made by separate molds. In case that a vehicle is different in kind and the radiator has different number of tubes, the different molds are used to manufacture the header and the tank.
In order to overcome the problems, the radiator having an aluminum tank has been introduced. Using the aluminum tank, parts of the tank are easy to manufacture, and components of the radiator are assembled temporarily and then brazed to complete the radiator, whereby a calking process is not required.
In addition, the header and the tank are made of the same material and thus are easy to recycle. The header and the tank joined by a brazing are excellent in strength and durability.
However, the aluminum tank has to satisfy the following requirement.
Firstly, the aluminum tank has to be simple in shape. The tank having a complicated shape is difficult to be compatible with various kinds of vehicles, leading to a high manufacturing cost.
Secondly, since the aluminum tank is coupled to the header by the brazing, a coupling force between the aluminum tank and the header is stronger than in the plastic tank, and a crack does not occur in the tank. But, the aluminum tank has to have a strength as strong as the plastic tank without increasing a coupling force of other parts and a material thickness.
Thirdly, the upper and lower tanks have to be used commonly. Since the plastic tank is formed by an injection molding together with most appendages, the upper and lower tanks differ necessarily in shape. However, in case of the aluminum tank, since all appendages are made separately and then attached to the tank, the upper and lower tanks have to have the same shape.
Fourthly, the aluminum tank has not to be transformed. The aluminum tank is not broken but can be transformed permanently due to an inner pressure. Such a transformation can be prevented by increasing a material thickness of the tank and varying a size of the tank. However, when a thickness of the tank is increased, a manufacturing cost is increased, and a size of the tank becomes small. As a result, a performance of the radiator can be lowered. Therefore, the aluminum tank has not to be transformed without increasing a thickness thereof.
Japanese Patent Publication Nos. 11-118386 and 2000-220988 disclose an aluminum radiator having an aluminum tank. However, the aluminum radiator does not consider fundamental shortcomings such as a transformation volume of the radiator according to a pressure drop, and a size of the radiator determining its performance at all.
Therefore, there is a need for an aluminum radiator that can minimize a transformation volume of the radiator and have an optimum size of maximizing its performance.
FIG. 4 is a perspective view of a conventional aluminum radiator. FIG. 5 is a cross-sectional view of the conventional aluminum radiator.
The aluminum radiator 10 includes a header tank 20 and 30, a core 40 and a support 50.
The header tank 20 includes a pair of header 21 spaced apart from each other, a tank 22 coupled to a pair of the header 21 by a brazing and having a heat exchange medium passage formed therein, and end caps 23 coupled to both opening portions of the header 21 and the tank 22. The header tank 30 has the same configuration as the header tank 20, and thus its description is omitted to avoid a redundancy.
The core 40 includes a plurality of tubes 41 and fins 42 arranged between the tubes 41. The tube 41 is coupled to a pair of the header 21 and communicates with the passage of the tanks 22. A heat exchange medium flows through the tube 41.
The support 50 is coupled to the headers 21 to support the most outer tube among the tubes 41.
The header 21 includes a flat portion 21a having a predetermined length and a tank coupling portion 21b bent from both ends of the flat portion 21a. The tank 22 includes a ceiling portion 22a having a predetermined length and a header coupling portion 22b bent from the ceiling portion 22a. The header coupling portion 22b of the tank 22 is coupled to the tank coupling 21a of the header 21.
Meanwhile, in the state that the header 21, the tank 22 and the core 40 are temporarily assembled, the aluminum radiator 10 is laid on a conveyer C of a high-temperature brazing furnace and is conveyed, and the aluminum radiator 10 is brazed while conveyed.
However, as shown in FIG. 5, the aluminum radiator 10 gets to have a step difference H1 between the conveyer C and the header coupling portion 22b when laid on the conveyer C. A covering between the tank coupling portion 21b and the header coupling portion 22b is melted due to a high-temperature brazing furnace while conveyed, and thus the tank 22 becomes sagged due to its weight as described by a dotted line. Consequently, a contact portion between the tank coupling portion 21b and the header coupling portion 22b is not perfectly brazed.
A phenomenon that the header coupling portion 22b is sagged from the tank coupling portion 21b is slightly suppressed due to the end caps 23 coupled to both opening portions of the header tank 20. However, since a supporting force of the end caps 23 is much weaker than a sagging force of the tank 22, the completed radiator 10 has defects.
In order to prevent the tank 22 from sagging, a jig is interposed between the header coupling portion 22b and the conveyer C to settle the step difference H1. However, it is difficult to arrange the jig at an accurate location, and it is also inconvenient, thereby lowering a productivity.